The closing device forms a pilot-controlled valve. Such a valve is particularly used in connection with the control of water, which is exposed to a high pressure. Applications are, for example, car washing plant and fire fighting systems. Also in the field of water hydraulics such a valve can be used.
The mode of operation is relatively simple. Pressure from the inlet connection reaches the second pressure chamber through the throttle and acts upon the valve element with a force, which presses the valve element against the valve seat. Additionally, the force of the resetting device acts upon the valve element in the closing direction, so that the valve element bears on the valve seat. The pressure ruling in the first pressure chamber can exert no force on the valve element, which is sufficient to lift the valve element from the valve seat.
When the auxiliary valve, which acts as a pilot valve, is activated and opens the channel arrangement, the pressure in the second pressure chamber drops to approximately the pressure at the outlet connection. The fluid flows off from the second pressure chamber. Fluid is resupplied to the second pressure chamber through the throttle. Together with the pressure drop at the throttle, the pressure in the first pressure chamber is now sufficient to overcome the force of the resetting device, and the valve element lifts off from the valve seat under the effect of the pressure in the first pressure chamber and the pressure drop at the throttle.
However, with such valves, heavily varying performances have been established during opening. In some cases, the valve element does not lift sufficiently off from the valve seat, so that the desired flow is not released. The valve can then not work with full capacity.